Some Mercedes (all of my 124/201s made after '84 on) can be locked/unlocked from the trunk. Not sure about a 123, but worth a try.
124/201, and later 126/107 all have the single-line unlocks-from-any-lock electric pump system. But not the 123. (Nor the 114, 115 or 116 either.)
You may be able to open the trunk with the new VIN key and from there you can access the locking and unlocking vacuum hoses, but I'm not sure you can apply enough vacuum to one of them to actually open the locks due to the action of the vent orifice in the driver's-door vacuum switch. -- Jim
